Physiological Changes during the Process of Pericarp Browning in the Postharvest Litchi

[Objective] Pericarp browning in the postharvest litchi significantly reduced its commercial value and limited the expanding of litchi markets. Physiological changes during the process of pericarp browning were determined in order to identify the underlying mechanisms. [Method] Matured Feizixiao fruits were stored at 25 ℃ and 70%±5% relative humidity. The physiological changes happened in pericarp during storage were tested at an 8-hour interval. [Result] The fruit of Feizixiao (Litchi chinensis Sonn. cv Feizixiao) turned completely brown within 72 h after being harvested under the experimental conditions. Sharp increase of the browning index occurred from 48 to 64 hours after harvest (HAH). With the browning of pericarp,water content of the whole fruit and pericarp decreased continuingly. In contrast,there were no significant changes in the water content of pulp during the same period. MDA content,pH value and relative leakage rate of pericarp were increased during storage. Most of pigment contents including anthocyanin,flavonoid,phenols,chlorophyll a and total chlorophyll decreased. POD activity was initially increased in 32 HAH and then decreased afterwards. PPO activity was decreased continuously,while the activities of catalase and superoxide dismutase exhibited the pattern of 'increasing-decreasing-increasing' as the storage time progressed. Correlation,stepwise regression and path analyses showed that water loss of pericarp was the major factor of pericarp browning. Principal and cluster analyses showed that there were two stages of pericarp browning during the course of litchi storage. [Conclusion] Water status of pericarp was the most important factor affecting pericarp browning. The pericarp browning happened by stages,which was mainly determined by the water loss of pericarp.

Prevalence of vegetation browning in China’s drylands under climate change

Vegetation greening has long been acknowledged,but recent studies have pointed out that vegetation greening is possibly stalled or even reversed.However,detailed analyses about greening reversal or increased browning of vegetation remain scarce.In this study,we utilized the normalized difference vegetation index(NDVI)as an indicator of vegetation to investigate the trends of vegetation greening and browning(monotonic,interruption,and reversal)through the breaks for the additive season and trend(BFAST)method across China’s drylands from 1982 to 2022.It also reveals the impacts of ecological restoration programs(ERPs)and climate change on these vegetation trends.We find that the vegetation displays an obvious pattern of east-greening and west-browning in China’s drylands.Greening trends mainly exhibits monotonic greening(29.8%)and greening with setback(36.8%),whereas browning shows a greening to browning reversal(19.2%).The increase rate of greening to browning reversal is 0.0342/yr,which is apparently greater than that of greening with setback,0.0078/yr.This research highlights that,under the background of widespread vegetation greening,vegetation browning is pro-gressively increasing due to the effects of climate change.Furthermore,the ERPs have significantly increased vegetation coverage,with the increase rate in 2000-2022 being twice as much as that of 1982-1999 in reveg-etation regions.Vegetation browning in southwestern Qingzang Plateau is primarily driven by adverse climatic factors and anthropogenic disturbances,which offset the efforts of ERPs.

Transcriptome and metabolome analysis of preharvest internal browning in Nane plum fruit caused by high temperature

The preharvest internal browning of Nane plum fruit,with no visible effects on the appearance of the fruit,has become a serious problem in recent years in its production area in Guangdong Province,China.This study investigated the effects of environmental factors,including temperature,on Nane plum internal browning.Plum orchards at different elevations with different incidences of internal browning were selected.Using fruits with different internal browning incidence levels,the internal browning mechanism was analyzed with transcriptome and metabolome analyses.The results revealed decreased internal browning at high altitudes.Shading treatment significantly reduced internal browning,whereas bagging and insect-proof net-covering treatments significantly increased internal browning.Because bagging and net coverings increase the local ambient temperature,the findings suggest that high temperature is an important factor influencing the internal browning of Nane plum.The metabolome experiments showed that with increased internal browning,the levels of phenolic hydroxyls such as catechol increased,with simultaneous increases in hydrogen peroxide content and oxidase activity.It can be speculated that the oxidation of phenolic hydroxyl substances is the main cause of the preharvest browning of Nane plum.Transcriptome analysis revealed the increased expression of calcium signaling-related and downstream effector genes and indicated an important role of calcium in internal browning,possibly due to its increased content in the fruit.Further,with increasingly serious internal browning,genes related to photosynthesis were down-regulated,while genes related to senescence were up-regulated,thus suggesting the up-regulation of the process of cell senescence during internal browning.In conclusion,heat stress should be eliminated to reduce preharvest internal browning in Nane plum.

Ekphrasis in Robert Browning’s “Fra Lippo Lippi”

As an ekphrastic poem re-created from the painting Coronation of the Virgin,“Fra Lippo Lippi”lacks adequate scrutiny from the perspective of interart poetics.With regards to the core concept of ekphrasis,this paper makes an in-depth analysis of the features and functions of ekphrasis in the poem.The former lie in the poet’s identification with the painter,and his imaginative supplementation in“the verbal representation of visual representation”.The latter are embodied in the revelation of the invisible in the painting,namely,the desires and value of human beings,as well as the power of beauty and truth.Browning enriches the poem with both philosophical and artistic contemplation,thus strongly conveying the thematic implications of“know thyself”and the persistent pursuit of beauty and truth.It is hoped that this study can shed some light on the studies of Robert Browning and the poem itself,and contribute to the development of the interart poetics.

Resistance index and browning mechanism of apple peel under high temperature stress

Apples are one of the most important economic crops worldwide.Because of global warming and an aggravation of environmental,abnormally high temperatures occur frequently in fruit-growing season and seriously affect normal fruit growth and reduce fruit quality and yield.We took five-year-old Ruixue’(Qinfu 1×Pink Lady;CNA20151469.1) fruits as test materials,and the ambient temperature during fruit development was monitored.The results showed that during the fruit-growing season,especially during the rapid growth stage (July to August),the maximum daily temperature exceeded 30℃ and lasted for more than 40 days.To determine the effects of high temperature stress on the apple fruit resistance,we treated expanding,veraison,and maturity-period fruits at different temperatures.It was found that the fruits of the expanding period showed strong resistance to high temperature stress,whereas during veraison and maturity,fruit resistance to high temperature stress decreased,and the fruit peel browning phenotype appeared.Meanwhile,the content of malonaldehyde (MDA),hydrogen peroxide (H_(2)O_(2)),and superoxide anion (O._(2)^(-)) in the peel gradually increased with increasing temperature.The content of total phenols,flavanol,and flavonoids in the peel decreased substantially at 45℃.Moreover,it was found that polyphenol oxidase gene (MdPPO1) was most sensitive to high temperature stress in apple.Furthermore,transient and stable MdPPO1 overexpression significantly promoted peel browning.The transgenic materials were more sensitive to high temperatures,and browning was more severe compared to non-genetically modified organism (WT).Stable MdPPO1 knockout calli obtained via clustered regularly interspersed short palindromic repeats (CRISPR/Cas9) gene knockout technology reduced the browning phenotype,and the resultant fruits were not sensitive to the effects of high temperature stress.Thus,MdPPO1 expression may be a key factor of high temperature-related changes observed in the browning phenotype that provides a scientific theoretical basis for the selection of high temperature-resistant varieties and apple cultivation and management in the future.

Comparative histology,transcriptome,and metabolite profi ling unravel the browning mechanisms of calli derived from ginkgo(Ginkgo biloba L.)

Gingko biloba accumulates high levels of secondary metabolites of pharmaceutical value.Ginkgo calli develop a typical browning that reduces its regenerative capacity and thus its usefulness.To elucidate the browning mechanism,histological,transcriptomic,and metabolic alterations were compared between green and browning calli derived from immature ginkgo embryos.Histological observations revealed that browning calli had a more loosely arranged cell structure and accumulated more tannins than in green calli.Integrated metabolic and transcriptomic analyses showed that phenylpropanoid metabolism was specifi-cally activated in the browning calli,and 428 diff erentially expressed genes and 63 diff erentially abundant metabolites,including 12 fl avonoid compounds,were identifi ed in the browning calli compared to the green calli.Moreover,the expression of fl avonol synthase(FLS)and UDP-glucuronosyl-transferase(UGT)genes involved in the fl avonoid pathway was more than tenfold higher in browning calli than in green calli,thus promoting biosynthesis of fl avonol,which serves as a substrate to form glycosylated fl avonoids.Flavonoid glycosides constituted the major coloring component of the browning calli and may act in response to multiple stress conditions to delay cell death caused by browning.Our results revealed the cellular and biochemical changes in browning callus cells that accompanied changes in expression of browning-related genes,providing a scientifi c basis for improving ginkgo tissue culturability.

Widely Untargeted Metabolome Profiling Provides Insight into Browning and Nutritional Quality Changes in Short-Term Stored Fresh-Cut Potato(Solanum tuberosum L.)Shreds

Potato(Solanum tuberosum L.)is susceptible to enzymatic browning after fresh processing,resulting in color change and potential alteration in the nutritional quality.In this study,a popular potato cultivar,Feiwuruita,was used to profile the metabolites involved in color and nutritional quality changes in fresh shreds stored at 0 and 4 h at 25°C(designated CK and CK4H,respectively).The shreds turned brown within 4 h of storage.In all,723 metabolites consisting 12 classes of compounds were detected in the samples,largely lipids,phenolic acids,alkaloids,amino acids and derivatives,flavonoids,organic acids,nucleotides and derivatives.Of these,163 metabolites accumulated differentially between CK and CK4H shreds.Polyphenolic compounds(phenolic acids and flavonoids)mostly increased in the shreds after 4 h storage.Conversely,the short-term storage drastically reduced lipid compounds(25 LysoPC and 19 LysoPE),while essential alkaloids and terpenoid compounds that are beneficial to human health increased in accumulation.The findings present global metabolome and nutritional composition changes in short-term stored shreds of Feiwuruita.This study provides important foundation for future studies on browning prevention/reduction and for better utilization of Feiwuruita.

Ginsenoside F1 administration promotes UCP1-dependent fat browning and ameliorates obesity-associated insulin resistance

Obesity-induced type 2 diabetes is mainly due to excessive free fatty acids leading to insulin resistance.Increasing thermogenesis is regarded as an effective strategy for hypolipidemia and hypoglycemia.Ginsenoside is a natural active component in Panax ginseng C.A.Meyer,and some of them enhance thermogenesis.However,there are few studies on the mechanism and target of ginsenosides enhancing thermogenesis.Using thermogenic protein uncoupling protein 1(UCP1)-luciferase reporter assay,we identifi ed ginsenoside F1 as a novel UCP1 activator in the ginsenosides library.Using pull down assay and inhibitor interference,we found F1 binds toβ3-adrenergic receptors(β3-AR)to enhance UCP1 expression via cAMP/PKA/CREB pathway.We also investigated the ability of F1 on energy metabolism in obesity-induced diabetic mice,including body weight,body composition and energy expenditure.The results of proteomics showed that F1 signifi cantly up-regulated thermogenesis proteins and lipolytic proteins,but down-regulated fatty acid synthesis proteins.Ginsenoside F1 increased thermogenesis and ameliorated insulin resistance specifi cally by promoting the browning of white adipose tissue in obese mice.Additionally,ginsenoside F1 improves norepinephrine-induced insulin resistance in adipocytes and hepatocytes,and shows a stronger mitochondria respiration ability than norepinephrine.These fi ndings suggest that ginsenoside F1 is a promising lead compound in the improvement of insulin resistance.

AcbHLH144 transcription factor negatively regulates phenolic biosynthesis to modulate pineapple internal browning

Internal browning(IB),a major physiological disorder of pineapples,usually happens in postharvest processes,but the underlying mechanism remains elusive.The bHLH transcription factors are involved in regulating various biological processes,but whether they could regulate tissue browning in fruit during storage remains unknown.Here we showed that the phenolic biosynthesis pathway was activated in pineapples showing IB following 9 days of storage.AcbHLH144 expression was the highest of the 180 transcription factors identified,downregulated in pineapple with IB,and negatively correlated with the major phenolic biosynthetic genes.AcbHLH144 was shown to be localized in the nucleus and its transient overexpression in pineapples and overexpression in Arabidopsis decreased phenolic biosynthesis.The yeast one-hybrid assay and electrophoretic mobility shift assay showed that AcbHLH144 directly bound to the Ac4CL5 promoter and the dual-luciferase reporter assay showed that it inactivated Ac4CL5 transcription.These results strongly suggest AcbHLH144 as a repressor for phenolic biosynthesis.Abscisic acid(ABA)alleviated IB,reduced phenolic accumulation,and downregulated phenolic biosynthetic genes,including Ac4CL5.Transcriptomic analysis showed that AcbHLH144 was the most upregulated of all 39 bHLHs in response to ABA.ABA enhanced AcbHLH144 expression,reduced phenolic contents,and downregulated phenolic biosynthetic genes in pineapples transiently overexpressing AcbHLH144.Moreover,ABA enhanced enzyme activity of GUS driven by the AcbHLH144 promoter.These results showed that AcbHLH144 as a repressor for phenolic biosynthesis could be activated by ABA.Collectively,the work demonstrated that AcbHLH144 negatively regulated phenolic biosynthesis via inactivating Ac4CL5 transcription to modulate pineapple IB.The findings provide novel insight into the role of AcbHLH144 in modulating pineapple IB during postharvest processes.

Effects of dry fog humidification on pericarp browning and quality of litchi fruit stored at low temperature

Pericarp browning is the major cause of deterioration of harvested litchi fruit.Water loss plays a role in pericarp browning of litchi fruit.This study investigated the effects of humidification with dry fog on pericarp browning and quality of litchi fruit stored at low temperature.Litchi fruit were stored in a non-humidified cold chamber(control)or in a humidified cold room using Tabor atomizer system that generated 95%relative humidity(RH)without depositing water on the fruit surface at 4℃.Control fruit stored in cold room without added humidity underwent rapid weight loss,accompanied by severe pericarp browning after 25 d of storage.However,slight weight loss and no obvious pericarp browning were found in humidified-fruit.Moreover,humidification maintained well the integrity of cell membrane and inhibited polyphenol oxidase activity during early storage.In addition,respiration rate was obviously inhibited in humidified-fruit compared with control fruit.This study might provide a convenient approach to reduce pericarp browning of harvested litchi fruit by humidifying the fruit using the Tabor atomizer at low temperature instead of packaging with film.

Variation Law of Pericarp Tenderness of Super Sweet Corn Kernel

To investigate the variation law of pericarp tenderness in growth progress of super sweet corn kernel, the values of pericarp tenderness of 10 super sweet corn inbreeds were measured during kernel growth, and the variations under differ- ent conditions were analyzed. The results showed that there existed gradient differ- ences in pericarp tenderness among the 10 materials, of which PE10 had the best pericarp tenderness, T105 took medial place, and $33205 performed worst in peri- carp tenderness. Pericarp tenderness values of these 3 inbreeds increased curvedly from 12 to 24 days after pollination, in the spring （Wuhan, Hubei） and winter （Ling- shui, Hainan） of 2014. Moreover, the average pericarp tenderness at different time points presented the same decreasing order of $33205, T105, PE10, which was not altered by enviroment. With the growth of kernel, for one material, the difference of pericarp tenderness under different environments presented a law of increment, re- duction, uniformity. As for optimum-picking time, there was four days difference be- tween the spring in Wuhan and winter in Lingshui. However, there was no obvious difference in pericarp tenderness on the optimum picking time, which indicated that growing environment could affect the variation ratio of pericarp tenderness, but it still depended on the nature of materials.

Two new diarylheptanoids from the pericarps of Juglans regia L.

Two new cyclic diarylheptanoids juglanin A （1） and juglanin B （2） were isolated from the pericarps of Juglans regia L. Their structures were elucidated by various spectroscopic methods including 2D NMR techniques （COSY, HMQC, HMBC, NOESY） and HR-ESIMS.

Difference in volatile profile between pericarp tissue and locular gel in tomato fruit

Aroma, a complex mixture of volatile compounds, plays an important role in the perception and acceptability of tomato products by consumers. Numerous studies have reported volatile profiles in tomatoes based on measurement of the whole fruit or pericarp tissue, however, little is understood regarding the volatile compositions in the inner tissues. The objective of this study was to investigate the differences in volatile profile between pericarp tissue and Iocular gel in tomato fruit. Based on HS-SPME-GC-MS analysis, totally 42 volatile compounds were detected in FL 47 and Tasti-Lee tomato fruits. Regardless of cultivars, a substantial higher concentration of total volatile compounds was observed in pericarp than that in/ocular gel, associated with higher levels of aldehydes, hydrocarbons, and nitrogen compounds. Pericarp tissue possessed higher levels of cis-3-hexenal, hexanal, heptanal, octanal, nonanal, cymene, terpinolene, undecane, dodecane, 2-phenylethanol, 6-methyl-5-hepten-2-one, 2-methylbutyl acetate, 1-nitro-pentane, and 1-nitro-2-phenylethane, while the abundances of 2-methylpropanal, butanal, 2-methylbutanal, 2-methyl-2-butenal, 2-methylpropanol, 3-methylbutanol, 2-methylbutanol, and 2-butanone were higher in Iocular gel. Principal component analysis （PCA） and cluster analysis using GC-MS and electronic nose （E-nose） data discriminated the two tissues.

Study on the Browning in Cell Suspension Culture of Taxus cuspidata

[Objective] This study aimed to investigate the browning of T. cuspidata cells in suspension culture and provide the guidance for the cell suspension culture of T. cuspidata. [Method] T. cuspidata callus was used as experimental materials, to explore the effect of different medium, N/P ratio, pH, shaking speed, illumination time and light intensity and other factors on browning of T. cuspidata cells in suspension culture. [Result] Non-browning callus was transferred to 2MB5 medium （pH 7.0） for illumination culture at 22℃ under light intensity of 1 500 lx with shaking speed of 90 r/min for 24 h. Results showed that the cell browning was significantly inhibited. [Conclusion] This study laid the foundation for cell suspension culture of T. cuspidata and had important significance to the large-scale industrial production of paclitaxel.

Construction of Near Isogenic Lines for Pericarp Color and Evaluation on Their Near isogenicity in Rice

The inheritance of purple pericarp was studied through genetic analysis using F2, BC1F1 and F3 from a cross between a purple pericarp rice variety Zixiangnuo and a white pericarp rice variety Chunjiangnuo 2. Seven pairs of near isogenic lines （NILs） for pericarp color of rice were further constructed. Genetic analysis indicated that the purple pericarp was controlled by two complementary genes （Pb and Pp）. Agronomic trait analysis and polymorphism analysis using SSR markers on these seven pairs of NILs were used in the evaluation of near-isogenicity. No significant differences in agronomic traits were found except 1000-grain weight between the NILs. The polymorphic SSR markers for the parents were only detected in target segments of the five pairs of NILs different in Pb, which revealed the ideal near isogenicity of them. However, for the two pairs of NILs different in Pp, the polymorphic markers for the two parents were detected as well as in non-targeted segments of chromosomes 11 and 12, respectively.

A Study on the Ultrasonic Extraction and Antioxidant Activity of Lychee Pericarp Polysaccharides

The aim was to optimize ultrasonic extraction conditions and study antioxidant activities of lychee pericarp polysaccharides. The effects of extraction temperature,time,ultrasonic power,solid-liquid ratio on polysaccharides yield were investigated by single-factor experiment and orthogonal experiment to obtain optimum extraction conditions; the antioxidant activities of lychee pericarp polysaccharides were evaluated by the total antioxidant activity. Optimum extraction process was under extraction temperature of 80 ℃,extraction time of 2. 5 h,ultrasonic power of 180 W,solid-liquid ratio of 1∶ 25 g / m L; the total antioxidant activity was increased with the increasing concentration of polysaccharides. The extraction process is simple and efficient. The extraction rate of lychee pericarp polysaccharides with antioxidant activities is high.

Validation of the Red Pericarp Gene from 419 Rice Landraces in Guangxi via Genome-wide Association Studies

Rice has different colors of pericarp, such as red, white and black. Red rice pericarp is rich in proanthocyanins, which have antioxidant properties and are beneficial to human health. In the present study, we analyzed the red-pericarp gene Rc of 419 rice landraces in Guangxi by genome-wide association study （GWAS）, and validated that the Rc gene regulated the red periearp trait in flee. By analyzing the genomie DNA of 97 red-pericarp flee eultivars, we identified two new alleles in C139 and C323. Then, the exons of Rcc＇9 and Rcc were sequenced with Sanger method, and the results demonstrated that the natural mutations within Re ene resulted in the two alleles Rcc and Rcc.

Effect of Postharvest Heat Treatment on Pear Browning during Storage

The effect of postharvest heat treatment on browning of Huangguan pear was investigated. The results showed that heat treatment improved hardness and soluble solid content of stored pear fruit, postponed the improvement of MDA content and PPO activity in stored pear fruit and alleviated the reduction of SOD activity and the lowering of PG activity. To sum up, heat treatment reduces the occurrence of browning of stored pear fruit through the regulation of the changes in a series of physiological and biochemical indexes of fruit.

Effects of grape seed extract on meat color and premature browning of meat patties in high-oxygen packaging

This study investigated the effects of grape seed extract(GSE)on fresh and cooked meat color and premature browning(PMB)in ground meat patties(85% beef and 15% pork back fat)packaged under high-oxygen modified atmospheres(HiOx-MAP).The GSE was added to patties at concentrations of 0,0.10,0.25,0.50 and 0.75 g kg^(-1).This study evaluated the surface color,pH,lipid oxidation,and total viable counts(TVC)of raw patties,and the internal color and pH of patties cooked to a temperature of 66 or 71℃ over 10-day storage at 4℃.Compared with the control(0 g kg^(-1) GSE),GSE improved the color stability(P<0.05)and significantly inhibited the lipid and myoglobin oxidation of raw patties from day 5 to 10,but GSE had no effect(P>0.05)on TVC.Patties containing 0.50 and 0.75 g kg^(-1) GSE cooked to 66℃ exhibited greater(P<0.05)interior redness than the control and reduced the PMB of cooked patties in the late storage stage.These results suggested that 0.50 and 0.75 g kg^(-1) GSE can improve fresh meat color and minimize PMB of HiOx-MAP patties.

Optimizing the Extraction of Anthocyanins from Pitaya(Hylocereus undatus)Pericarp

[Objectives]This study was conducted to confirm the existence of anthocyanins in pitaya(Hylocereus undatus)pericarp and optimize the extraction condition.[Methods]Single-factor tests were carried out on five factors:ethanol concentration,extraction temperature,ultrasonic power,solid-to-liquid ratio and extraction time.Based on the single-factor test results,four factors and three levels of process conditions were optimized by Box-Behnken design test.[Results]Anthocyanins exist in the pericarp of pitaya,and the optimum conditions were extraction temperature 49℃,ultrasonic power 120 W,extracted time 2 h and ethanol concentration 60%.Under these conditions,the average yield of anthocyanins was 80 mg/100g.[Conclusions]This study provides a theoretical basis for the extraction of anthocyanins from the pericarp of red-flesh pitaya.